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Multi-receiver satellite positioning system method and system for improved performanceMulti-receiver satellite positioning system method and system for improved performance description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070132636, Multi-receiver satellite positioning system method and system for improved performance. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] This invention relates generally to Satellite Positioning System (SPS) devices, and more particularly to a method and system for using SPS receivers to improve performance. BACKGROUND OF THE INVENTION [0002] An SPS system such as the Global Positioning System (GPS) has 24 satellites orbiting the earth (21 operational and 3 spares). These satellites are arranged into 6 high orbit planes at a height of 10,898 nautical miles or 20,200 kilometers with each orbit containing three or four satellites. The orbital planes form a 55 degree angle with the equator with orbital periods for each satellite of approximately 12 hours. [0003] With no obstruction, there are typically 8-12 satellites visible at any one time from anywhere on earth. Each satellite contains a highly accurate (Rubidium atomic) clock. Taken together, several GPS satellites can represent an extremely accurate time standard available for synchronization at any point on the earth. It is this accurate timing that leads to an application of the GPS satellites separate from their function for navigation. The world's cellular and fiber communications use the time information derived from the GPS satellites for clock synchronization. Each satellite transmits a spread spectrum signal containing a BPSK (Bi-Phase Switched keyed) signal in which 1's and 0's are represented by reversal of the phase of the carrier. This message is transmitted at the L1 frequency 1575.42 MHz at a "chipping rate" of 50 bits per second. The message repeats every 30 minutes and is called the C/A signal (Coarse Acquisition signal). This message contains two important elements, the almanac and the ephemeris. The Almanac contains information about all the satellites in the constellation. This information is regularly updated from ground stations monitoring the system but almanac data remains useful for around one year. The Ephemeris contains short-lived information about the constellation and the particular satellite sending it. The particular satellite's information is updated from the GPS ground stations every four hours. Its validity in calculating position deteriorates gradually over this period as satellites rise and fall above the horizon. There are also other encrypted signals: the P code and Y code that are used for military applications transmitted at frequencies L1 & L2. [0004] GPS signals are typically weak and require a radio frequency (RF) front end that has a low noise figure and very high gain. To derive a position solution including altitude, the GPS receiver must acquire and receive a full set of ephemeris from 4 or more satellites to compute a solution. The transfer of ephemeris from the GPS satellites is relatively slow (noted above as 50 bps), so alternative transmissions sources (such as a cell phone networks) have been used to send ephemeris and frequency uncertainty information to enable a GPS handset to compute a solution more expeditiously. [0005] GPS is an example of a satellite position system (SPS) that may be utilized by a wireless device in combination with an appropriate GPS receiver to pinpoint the location of the wireless device on earth. The array of GPS satellites transmits highly accurate, time coded information that permits a receiver to calculate its exact location in terms of latitude and longitude on earth as well as the altitude above sea level (when 4 or more GPS satellites are acquired). The GPS system is designed to provide a base navigation system with accuracy to within 100 meters for non-military use and greater precision for the military. [0006] As mentioned above, each of the orbiting satellites contains accurate clocks and more particularly four highly accurate atomic clocks. These provide precision timing pulses used to generate a unique binary code (also known as a pseudo random or pseudo noise "PN" code) that is transmitted to earth. The PN code identifies the specific satellite in the constellation. The satellite also transmits a set of digitally coded ephemeris data that completely defines the precise orbit of the satellite. The ephemeris data indicates where the satellite is at any given time, and its location may be specified in terms of a satellite ground track in precise latitude and longitude measurements. The information in the ephemeris data is coded and transmitted from the satellite providing an accurate indication of the exact position of the satellite above the earth at any given time. A ground control station updates the ephemeris data of the satellite once per day to ensure accuracy. [0007] A GPS receiver configured in a wireless device is designed to pick up signals from three, four, or more satellites simultaneously. The GPS receiver decodes the information and, utilizing the time and ephemeris data, calculates the approximate position of the wireless device. The GPS receiver contains a floating-point processor that performs the necessary calculations and may output a decimal display of latitude and longitude as well as altitude on the handset. Readings from three satellites are necessary for latitude and longitude information. A fourth satellite reading is required in order to compute altitude. [0008] Techniques that use cellular based location aiding information, however, still require a cellular network connection that may not necessarily be available within all of the areas within the footprint of the "viewable" GPS satellites. Thus, time to first fix (TTFF) times are usually relatively long. [0009] Even with some additional information, TTFF times may be over thirty seconds because the ephemeris data must be acquired from the SPS system itself, and the SPS receiver typically needs a strong signal to acquire the ephemeris data reliably. These characteristics of a SPS system typically impact the reliability of position availability and power consumption in wireless devices. Typically, the accuracy of location-based solutions may vary from 150 meters to 300 meters in these types of environments. As a result, locating a wireless device in a 300 meter radius zone is unlikely unless there are other methods to help narrow the search. [0010] Attempts at solving this problem have included utilizing pseudolites (such as base stations in a cellular telephone network) in combination with SPS, such as GPS, to determine the location of the wireless device. Other systems just use dual GPS to provide redundancy but do not necessarily share information to improve the performance of the other corresponding receiver. SUMMARY OF THE INVENTION [0011] Embodiments in accordance with the present invention can utilize information received from a secondary SPS receiver to aid in a similar manner as cellular phone networks and phone receivers have done or to alternatively provide an improved option among selected processed signals. Any SPS capable device such as a GPS receiver (and not necessarily limited to a GPS enabled cell phone) can use information from a secondary SPS receiver. [0012] In a first embodiment of the present invention, a multi-receiver satellite positioning system (SPS) radio can include a plurality of SPS receivers co-located with each other, and a processor coupled to a first SPS receiver and at least a second SPS receiver. The processor can be programmed to select a measurement from the first SPS receiver or from at least the second SPS receiver having a desired characteristic, and use the measurement selected for a predetermined application. The processor can select the measurement by comparing a possible error in position (EPE) reported by the first SPS receiver with a possible error in position reported by the at least second SPS receiver and selecting the measurement with the least amount of EPE. The processor can be further programmed to use for Location Based Services (LBS) a first position fix obtained among the plurality of SPS receivers. In another variation, the processor can be programmed to use for initial Location Based Services (LBS) processing a first position fix obtained among the plurality of SPS receivers and then subsequently use the measurement with the least amount of EPE for an LBS application. [0013] The desired characteristic can be a higher average signal strength from a plurality of SPS satellites or a larger number of satellites used in a positioning calculation or a higher average signal strength from a plurality of SPS satellites and a larger number of satellites used in a positioning calculation. Note, a position calculation can be done using the first SPS receiver concurrently with a position calculation using at least the second SPS receiver. In one alternative, the radio can comprise a single antenna coupled to the plurality SPS receivers. In another alternative, the radio can further include a first antenna coupled to the first SPS receiver and a second antenna coupled to at least the second SPS receiver. The desired characteristic can be a measurement providing better navigation performance than acquisition performance or alternatively a measurement providing better acquisition performance than navigation performance. The processor can also be programmed to share ephemeris data from a first reporting SPS receiver among the plurality of SPS receivers with at least a second SPS receiver in order to enable the second SPS receiver to achieve a faster time to fix. The processor can also be programmed to share almanac data from a first SPS receiver among the plurality of SPS receivers with at least a second SPS receiver [0014] In a second embodiment, a multimode cellular phone can include a first mode cellular transceiver having an first SPS receiver associated thereto, at least a second mode cellular transceiver having at least a second SPS receiver associated thereto, and a processor coupled to the first SPS receiver and at least the second SPS receiver. The processor can be programmed to select a measurement from the first SPS receiver or from at least the second SPS receiver having a desired characteristic and use the measurement selected. [0015] In a third embodiment, a method of improving position accuracy can include the steps of receiving positional assistance information from a plurality of satellite position system (SPS) satellites at a plurality of co-located SPS receivers, selecting among calculated measurements from each of the plurality of co-located SPS receivers based on a desired characteristic, and using a selected calculated measurement having the desired characteristic for a predetermined application. Selecting can be done by comparing a possible error in position (EPE) reported by a first SPS receiver with a possible error in position reported by at least second SPS receiver and selecting the measurement with the least amount of EPE for the predetermined application. Selecting can also be done by selecting among calculated measurements from each of the plurality of co-located SPS receivers based on a higher average signal strength from the plurality of SPS satellites and a larger number of SPS satellites used in a positioning calculation. Selecting can also be done by selecting among calculated measurements from each of the plurality of co-located SPS receivers based on a desired navigation performance or a desired acquisition performance. The method can also include the steps of sharing ephemeris data or almanac data from a first SPS receiver among the plurality of SPS receivers with at least a second SPS receiver. [0016] Other embodiments, when configured in accordance with the inventive arrangements disclosed herein, can include a system for performing and a machine readable storage for causing a machine to perform the various processes and methods disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS [0017] FIG. 1 is a block diagram of a positioning system using a plurality of SPS receivers in accordance with an embodiment of the present invention. [0018] FIG. 2 is a flow chart illustrating a method of improving position accuracy in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE DRAWINGS [0019] While the specification concludes with claims defining the features of embodiments of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the figures, in which like reference numerals are carried forward. Continue reading about Multi-receiver satellite positioning system method and system for improved performance... Full patent description for Multi-receiver satellite positioning system method and system for improved performance Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Multi-receiver satellite positioning system method and system for improved performance patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Multi-receiver satellite positioning system method and system for improved performance or other areas of interest. ### Previous Patent Application: Method for ephemeris assisted global positioning Next Patent Application: Method and apparatus for installing and/or determining the position of a receiver of a tracking system Industry Class: Communications: directive radio wave systems and devices (e.g., radar, radio navigation) ### FreshPatents.com Support Thank you for viewing the Multi-receiver satellite positioning system method and system for improved performance patent info. IP-related news and info Results in 0.15862 seconds Other interesting Feshpatents.com categories: Daimler Chrysler , DirecTV , Exxonmobil Chemical Company , Goodyear , Intel , Kyocera Wireless , 174 |
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